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Tolerancing not Changing Output

  • 1 November 2023
  • 5 replies
  • 76 views
C

I've been performing a tolerance analysis on some of my designs. In my tolerance results, I ran into a bug where the output is always the nominal value. I verified that the output should change by adjusting the values in the LDE. However, when I run the Monte Carlo or sensitivity analysis there is no change. 


Example: My TDE contains TTHI to change the distance from object to lens. My merit function contains operand RSRE to find the RMS radius of the image. Nominal is 8.092mm, when I change the thickness to the extreme of the tolerances in the LDE, the spot changes from 10.322mm to 5.773mm. So, I know that the thickness changes the spot. If I run the monte carlo, or sensitivity analysis with the criterion set to my merit function. The sensitivity says there is no change with TTHI, and the monte carlo only outputs 8.092mm (nominal). I recreated my file multiple times and sometimes operands work and sometimes they don't. Any ideas on what is happening?

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Best answer by Jeff.Wilde 2 November 2023, 20:20

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5 replies

Yang.Yongtao
Rank
Userlevel 2

Hi Chris

 did you set  any compensator in your sensitivity analysis?

 It will be better to upload your data 

 

Yang

Optics is interesting!
C

Hello Yang,

 

My final design will not have any tolerance compensation, so I am not using a compensator. I’m a little confused on how that will help.

 

Chris

C

 

Jeff.Wilde
Rank
Userlevel 7
Badge +3

@Chris.Ladas:

Try changing the “Adjust” parameter of your TTHI operand in the TDE to equal 1.  Your current setting of 0 means that surface 0 thickness is changing to compensate for your surface 1 thickness variation. 

 

See the help documentation for more detail:

 

Regards,

Jeff

Mark.Nicholson
Rank
Userlevel 7
Badge +3

It always helps to save files to examine exactly what is happening. You can put SAVE commands in the Tolerance Editor that will save a specific sensitivity, and you can save some number of randomly-generated Monte Carlo files. That way you can see exactly how the code is interpreting your inputs.

  • Mark

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